1. Field of the Invention
The present invention generally relates to input devices using an input pen, a touch panel, and the like used in personal computers, word processors, handy terminals, electronic notes, etc., and more particularly relates to an input device of a resistance layer type.
2. Description of the Prior Art
FIGS. 1A and 1B show an input panel of a resistance layer type of the prior art. As shown in FIGS. 1A and 1B, the input panel includes a lower board 1 and an upper board 2 which are provided on one surface thereof with transparent conductive layers 3 and 4, respectively. These two boards 1 and 2 are arranged such that the surfaces bearing the transparent conductive layers 3 and 4 face each other. Between the conductive layers 3 and 4, insulating spacers 5 are placed in a dot form or in a mesh form.
FIG. 2 shows a control circuit of the input panel of FIG. 1. As shown in FIG. 2, the upper conductive layer 4 is provided with X-coordinate electrodes 17 and 18, and the lower conductive layer 3 is provided with Y-coordinate electrodes 19 and 20. These electrodes are electrically connected as shown in FIG. 2.
When a pen and the like is pushed against the upper board 2 so as to establish an electrical contact between the upper conductive layer 4 and the lower conductive layer 3, X and Y coordinates of the contact location can be obtained. This panel can be provided on a display panel of a such device as a liquid crystal display (LCD) device, thus providing means for coordinate input.
In the input panel as described above, the two conductive layers 3 and 4 are arranged with a short gap therebetween held by the spacers 5, which gap is typically shorter than 14 .mu.m. Thus, there is optical interference between the two conductive layers 3 and 4, so that interference patterns as shown in FIG. 3 appear on the display. Such interference patterns hinder visibility of the display shown on the panel.
Accordingly, there is a need in the field of input panels for an input panel which can avoid the optical interference without degrading an input sensitivity of the input panel.